The present invention relates to a mobile lifting platform comprising a chassis as well as platform support means on which a first live ring or turntable is mounted. Said live ring has its vertical axis approximately centered on said platform and supports a horizontal boom for pivotal movement about said axis. On said horizontal boom in turn there is mounted a second live ring or turntable whose axis is offset from that of the first live ring. Moreover, a swivel structure is attached to said second live ring for pivotal movement about a vertical axis thereof, which swivel structure terminates in a boom carrying a platform or basket for workmen at its distal end.
Mobile lifting platforms of this type are in keeping with the proposed European standard prEN 280 of April 1994, as drafted by the "Technisches Komitee" (technical committee) CEN/TC 98/AG 1of the "Europaisches Komitee fur Normung" (European standards committee). Such mobile lifting platforms may be provided in the form of a trailer or as self-propelled machines.
Attempting to provide mobile lifting platforms which are short in total length and thus pose no maneuvering problems when used in traffic, complex multiple telescope systems as well as a pronounced bend of the swivel structure have been proposed in the prior art in order to make use of the area above the driver's cabin. Owing to the pronounced bend of the swivel structure, said structure--once swivelled--will exceed the overall width of the vehicle, thus projecting into the traffic area. Proximal support means are traditionally provided immediately behind the driver's cabin. As a consequence, the range or radius of the lifting means to the front must be limited in order to ensure steadiness and stability of the overall vehicle in operation.
A further disadvantage of the prior art is the common general necessity to use support means or stabilizers which may be telescopically extended or unfolded over the width of the vehicle since these likewise pose a traffic obstacle in operation, yet are required for operational safety.
German patent application DE 1,960,829 A1 discloses a mobile lifting platform with two live rings. The movement of said live rings is separately controlled via two drive units which are independent of each other. Such an arrangement is said to facilitate the reaching of positions which are outside the vehicle range.
It is the object of the present invention to provide a lifting platform of the aforementioned type in which fewer telescopic means are used with the same overall vehicle length and which facilitates movement of the lifting platform itself, at the same time leaving more space for passing traffic both when the lifting platform is being moved into position and when it is in operation.